Overload relay



April 30, 1946. G. c. ARMSTRONG 2,399,311

4 v OVERLOAD RELAY Original Filed April 1, 1942 WITNEssEs: l

. INVENTOR d leo/ye rmjfrong ATTORNEY Patented Apr. 30, 1946 OVERLOAD RELAY George C. Armstrong, Forest Hills, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Original application April 1, 1942, Serial No.

437,235. Divided and this application Octobe 23, 1943, Serial No. 507,437

11 Claims.

My invention relates to shock resisting overload relays, particularly those useful in protecting motors from excessive currents and is a division of my copending application Serial No. 437,235, entitled Overload relay, iiled April 1, 1942.

My invention more specifically relates to an overload relay having therein a tripping mechanism which includes, by way of example, a plurality of temperature responsive bimetals which upon predetermined heating actuate the tripping mechanism to trip the relay.

An object of my invention is to provide a thermal overload relay having therein a plurality of poles for protecting each phase of the system in which the relay is used.

Another object of my invention is to provide a solidly constructed relay capable of withstanding heavy shock.

, Another object of my invention is to provide a thermal overload relay which will not trip under heavy shock when carrying a large percentage of rated current.

A speciiic object of my invention is to provide a thermal overload relay having therein a plurality of poles for protecting each phase of the system in which the relay is used and having therein means for quickly tripping the relay in case of an open phase and after a predetermined time delay during normaloverload conditions.

Another object of my invention is to provide a thermal overload relay having therein an inertia element or latch to prevent tripping of the relay when subjected to mechanical shock.

Other objects and advantages will become more apparent from a study of the following specification when considered in conjunction with the accompanying drawings in which:

Figure 1 is a plan view of a relay embodying certain principles of my invention having plane movement for its tripping action,

Fig. 2 is an end view of Fig. 1,

Fig. 3 is a plan view of a relay having plane movement of its tripping mechanism and an inertia latch for resisting shock,

Fig. 4 is an end view oi Fig. 3, and

Fig. 5 is a fragmentary plan view of the tripping mechanism shown in Figs. 1 and 2 having an inertia element for resisting shock.

Referring now to the drawings there is illustrated in Figs. 1 and 2 an overload relay which provides quick single phase protection or tripping and tripping after a predetermined time delay during periods of normal overload. The entire relay is assembled upon a substantially rectangular base and comprises a pair of bimetal- ETI lic elements ||5 and which at one end are rigidly secured to the base and at the other end project through openings or windows provided in the catch element |33. This catch elementJ is slidably mounted on the base for vertical move ment and is biased upwardly against the restraining effort of the two bimetals by a spring |35.

ie bimetals are interconnected by means of an actuating rod of insulating material, Which rod also engages a latch member |23 pivotally mounted to the base at one end and at its other end engaging a free end |31 of the catch member |33, which is normally biased to engage the stationary contact |39, to maintain the contact in open position. Avprojection |4 is provided on the catch element |33 which upon predetermined movement of the catch engages an adjustable stop |43 secured to the base. This stop may be adjusted to either increase or decrease the distance of travel of the catch |33. Heaters |19 and |2| are provided for each of the bimetals and may be each connectedin one phase of the system to `be protected. Assuming upward deflection of the upper bimetal ||5 as caused by overheating due to an open phase, the actuating rod |25 being moved upwardly moves with it the latch |23 until a reduced end portion thereof |29 is adjacent a window or opening |3| in the catch element E33 at which time said latch quickly releases the catch |33 since the bottom bimetal being cold restrains the slidably mounted catch element |33 from moving upward under the influence of the compression spring |35. Releasing of the catch perN mits its free end |31 normally biased to engage the contact |39 completing a circuit through a relay coil to open the motor circuit (not shown).

AUnder normal overload conditions both bimetals I |5 and deflect upwardly. The sliclabl.r mounted catch element |33 is moved upwardly with the bimetals and latch by the compression spring |35 until projection |4| on said slidable catch element engages stop |43, adjustable for changing the relays rating, thus stopping the catch. Continued movement of the bimetals will then release the catch |33 and complete the relay circuit as before described.

As may be readily seen the type of relay shown in Figs. 1 and 2 is not necessarily limited to two poles but may have any number of poles that may be required by the system which it protects. With this embodiment of my invention, a bimetallic element may be provided for each phase in a system thus providing quick single phase protec tion in any case. Y

The relay illustrated in Figs. 3 and 4 differs from that of Figs. 1 and 2 in that quick single phase protection is not provided with a predetermined time delay for normal tripping. The bimetals are connected only to the latch element The latch element holds the contacts closed in this embodiment of the invention.

Relays of the type shown in Figs. l-4 are not inherently shock resisting. In order that this type may not trip during periods in which it is subjected to mechanical shock an inertia type of latch |45 has been added. This latch in Figs. 3 and 4 is pivotally mounted at |47 to the relay base and projects through a window or opening |49 in the trip latch |5|. The end projecting through the window is bent upwardly at right angles a suflicient distance that its upper end projects above the opening M9 in the trip latch. As may be seen in the drawings, the latch is first bent upwardly at an angle then nally at a right angle to the portion or the latch extending through the window. During normal tripping when the trip latch is deflected to the left, the lower surface of the inertia latch |45 follows the window edge upon which it rests dropping the upwardly extending portion of the latch down until it will clear the window and no longer obstruct travel of the trip latch to the tripping position. If, however, the relay were subjected to sudden shock from such a direction that the trip latch |5| would suddenly be deflected to the left, the inertia latch |45 in this instance due to the instantaneously high Velocity of trip latch movements will not move a substantial distance from its normal horizontal position and its upwardly extending edge will not clear the upper Window edge in the trip latch thus preventing the trip latch from reachits trip position. In this embodiment of my invention quick single phase protection is not to be had because the catch element is not slidably mounted. The distance the trip latch must travel before tripping takes place is, therefore, Xed for both single phase and normal overload tripping. Quick single phase tripping is accomplished, as shown in Fig. 5, by pivotally mounting the inertia latch at |43 to a slidably mounted catch member |33 similar to that of Figs. 1 and 2. The inertia latch |45 in that case would move with the catch member 33 and the trip latch |23 and thereby maintain a ii'xed position with respect to the trip latch.

I am, of course, aware that others, particularly after having had the benefit of the teachings of my invention, may devise other devices embodying my invention and I, therefore, do not Wish to be limited by the specic showing made in the drawings or the descriptive disclosure hereinbefore made, but wish to be limited only by the scope of the appended claims.

I claim as my invention:

l. A temperature responsive device comprising, in combination. a plurality of temperature responsive elements of the form of flat strips, tripping means comprising a latch member and a catch member supported and biased to move in a plane, movable contacting means controlled by said tripping means, means operatively relating the temperature responsive elements with the latch member and the catch member for effecting synchronized movement ofthe latch and catch members when all the temperature responsive elements are heated, one of said temperature responsive elements being effective to anchor said catch member and the remainder being effective to move the latch member relative to the catch member to tripping position when all but one of the temperature responsive elements are heated.

2. A temperature responsive device comprising in combination, a plurality of temperature responsive elements of the form of ilat strips, tripping means comprising a latch element and a catch element having plane movement for its tripping action, spring means for biasing said catch element in one direction in its plane of movement, movable contacting means controlled `by said tripping means, said temperature responsive elements being operatively related to said catch element for restraining movement thereof when the temperature responsive elements are unheated, means operatively relating the latch element with said temperature responsive element, said temperature responsive elements when all are heated effecting synchronized movement of the latch and catch elements, one of said temperature responsive elements being effective to anchor said catch element and the remainder being eflective to move the latch element to tripping position when all but said one of the temperature responsive elements are heated.

A thermally responsive device comprising, in combination, a plurality of thermally responsive elements of the form of flat strips, contacting means, tripping means for the contacting means comprising a latch member and a catch member having plane movement for its tripping action, said elements being each operatively related to the latch member and the catch member for effecting simultaneous movement or" the latch and catch members without movement therebetween when all said elements are heated, one of said elements being effective to anchor the catch member and the remainder being elrective to move the latch member to tripping position when all but one of the elements are heated, and an inertia latch for checking deflections of the latch member in the direction of tripping during periods of mechanical shock.

4. Apparatus as recited in claim 3, said inertia latch being pivo-tally mounted to said catch member for movement therewith and having the characteristic of pivoting from its latch position during slow deiiection of the latch member to allow the latch member to deilect to tripping position and maintaining its latch position to intercept the latch member during rapid deflection thereof during periods of mechanical shock.

5. A thermally responsive device comprising, in combination, a plurality of thermally responsive elements of the form of ilat strips, tripping means comprising a latch member and a catch member having plane movement tor tripping action, movable contacting means controlled by said tripping means, said elements being operatively related with said latch member to effect movement thereof relative to the catch member to operate the tripping means, and an inertia latch for checking deflections of the latch member in the direction of tripping during periods of mechanical shock.

6. Apparatus as recited in claim 5, said inertia latch being pivotally mounted to the base of said thermally responsive device and having the characteristic of pivoting from its latch position during slow deections of the latch member to allow the latch member to deflect to tripping position and maintaining its latched position to intercept the latch member during rapid deflection thereof during periods of mechanical shock.

7. In a thermal responsive device, the combination of contacting means, tripping means for the contacting means, said tripping means having a latch member and a catch member supported and biased to move in a plane, a plurality of thermally responsive elements operatively related With the latch and catch members to eiect movement thereof without movement therebetween when all said elements are heated, one of said elements being effective to prevent movement of the catch element and the other of said elements being effective to move the latch element to tripping position when all but said one of said elements are heated, and means for limiting the movement of said catch member to effect relative movement of the latch and catch members after predetermined movement of the catch member when all of said elements are heated.

8. Apparatus as set forth in claim 7 in which said means for limiting the movement of the catch member comprises an adjustable stop member operatively related to the catch member.

9. A thermally operated tripping mechanism comprising,r in combination, a latcli member, a catch member, means mounting the catch member for linear movement only, means biasing the catch member in one direction, means for limiting the movement of the catch member in said one direction, and a plurality of thermally responsive elements restraining said catch member against said biasing means and operatively associated with said latch memb'er.

10. A thermally operated tripping mechanism comprising in combination, a latch member, a catch member, means mounting the catch member for linear movement only, means biasing the catch member in one direction, means for limiting the movement of the catch member in said one direction, a plurality of thermally responsive elements restraining said catch member against said biasing means, and an inertia latch operatively related to both said members for preventing relative movement thereof during periods of mechanical shock.

l1. A thermally responsive tripping mechanism comprising in combination, a latch member, a catch member, means mounting the catch member for linear movement only, means biasing the catch member in one direction, means for limiting the movements of the catch member in said one direction, a plurality of thermally responsive elements restraining said catch member against said biasing means, and an inertia latch pivotally mounted on said catch member and positioned by said latch member to engage a cooperating portion of the latch member when the latch member is rapidly moved.

GEORGE C. ARMSTRONG. 

